THE 8-13 MICRON SPECTRUM OF ARP-299C

Arp 299C is a 5 x 10(10) L. infrared source in the merging galaxy system Arp 299. It is the most luminous object known that is not obviously associated with a galaxy nucleus. Our data show that the 8-13 mum spectrum of Arp 299C has a strong [Ne II] emission line and emission features like those of polycyclic aromatic hydrocarbon (PAH) molecules. These emission features are characteristic of H II regions associated with a burst of star formation. We did not detect any high-excitation ionic lines characteristic of an active galactic nucleus (AGN), nor a deep silicate absorption feature that might indicate a hidden compact nucleus. We deduce that Arp 299C is powered by an intense burst of star formation.